How do you know if a wine is cheap ?!
Answers: any indicators?
Assuming you are working with no more information than the glass of wine in front of you, and it is just a plain glass of wine that isn't flavored or infused with peach or something, it isn't easy to do.
The problem is that can buy a truly awful bottle of wine for $100 and a really good bottle for $6. Indicators of bad wine (like bubbles in your red wine, hints of skunk in the smell of your white) are not indicators of cheap. It's more likely that the wine was cheap, but by no means does bad equal cheap.
By the way, fabulous wine will turn your teeth purple just as quickly as bad wine.
Price tag
Well if it's in a box that is one sure sign
When it does not taste good.
If it's called Sneaky Pete or Thunderbird.
after taste.
measure the intensity of the headbanger the next morning!